1. Field of the Invention
The present invention relates to a refrigerant gas suction structure in a piston type compressor, which has pistons retained in a plurality of cylinder bores arranged around a drive shaft so that the pistons reciprocate with the rotation of the drive shaft, and which is suitable for an air conditioner in a vehicle.
2. Description of the Related Art
In a conventional piston type compressor (see Japanese Unexamined Patent Publication (Kokai) No. 3-92587, for example), suction ports respectively arranged between compression chambers and suction chambers are opened and closed by flapper type valves. The refrigerant gas in each suction chamber is drawn into the associated compression chamber through the associated flapper type valve which is forced open during the suction stroke of the piston moving from the top dead center to the bottom dead center. In the discharge stroke where the pistons move from the bottom dead center to the top dead center, the flapper type valves are closed, closing the suction ports. The refrigerant gas in the compression chamber is discharged through the discharge port, pushing the discharge valve, into the associated discharge chamber.
The opening and closing of the flapper type valves are caused by the pressure differences between the compression chambers and the suction chambers. When the pressure in the suction chambers is higher than that in the compression chambers, which occurs during the suction stroke of the pistons moving from the top dead center to the bottom dead center, the flapper type valves are bent or elastically deformed to open the suction ports.
The deformation of the flapper type valves acts as an elastic resistance against the movement of the respective suction valves. Accordingly, the flapper type valves will not open unless the pressure in the suction chambers becomes higher by some degree than that in the compression chambers. That is, the opening of the flapper type valves is delayed. A lubricating oil is suspended in the refrigerant gas in order to lubricate the internal components of the compressor. Thus, the lubricating oil is carried with the refrigerant gas to the necessary internal portions of the compressor. The lubricating oil can enter wherever the refrigerant gas flows, and will stick on the contact faces between the suction ports and the flapper type valves closing the suction ports. The sticking lubricating oil increases the contact force between the contact faces and the flapper type valves, further delaying the beginning of the deformation of the flapper type valves. This deformation delay reduces the flow rate of the refrigerant gas from the suction chambers into the compression chambers, or reduces the volumetrio efficiency. Further, even when the flapper type valves are opened, the elastic resistance of the flapper type valves also acts as a resistance against the suction of the refrigerant gas, thus reducing the flow rate of the refrigerant gas.